Groundwater Quality and Human Health Risk

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water Quality and Contamination".

Deadline for manuscript submissions: closed (20 April 2024) | Viewed by 22248

Special Issue Editor


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Guest Editor
Laboratory of Geoenvironmental Science and Environmental Quality Assurance, Department of Civil Engineering, University of West Attica, 250 Thivon & Petrou Ralli Str, Egaleo, 122 41 Athens, Greece
Interests: aquatic geochemistry; water quality; environmental geochemistry; geochemistry; geochemical modeling; contaminants transport; groundwater contamination; water quality indices; environmental monitoring and assessment; human health risk assessment
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Special Issue Information

Dear Colleagues,

One of the largest global resource problems to be faced in the coming years is access to safe water. Groundwater often requires less treatment and is therefore preferred over surface water as a source of drinking water. Utilizing groundwater as a sustainable resource requires the protection and preservation of suitable groundwater. Earth processes and geochemical processes occurring in the lithosphere, hydrosphere, biosphere, atmosphere, and anthroposphere control water composition and its use. Since groundwater travels through earth materials (rocks, sediments, soils), it can pick up geologically occurring trace elements or radionuclides. Agriculture, industry, human, and animal waste are among the most common sources of groundwater contaminants. Contaminant interactions in the subsurface system are affected, among others, by properties of earth materials, microbiological activities, and hydrogeological conditions.

In contrast to physical hazards (landslides, volcanoes, earthquakes), chemical hazards are challenging to accurately identify in space and time. Groundwater may contain chemical compounds that affect human health. If water intended for human consumption contains an unsafe level of chemical compounds, microbes, and radionuclides, it can cause severe health effects such as cancer, reproductive or developmental effects, skin discoloration, and organ damage. The main tools for determining the potential adverse effects of contaminants are evaluating human health risk and epidemiological studies. Meticulous research on contaminant redistribution from the land surface down to the water table plays a crucial role in delineating processes controlling groundwater quality. Most national authorities and stakeholders already have established standards for drinking water, including limits for several common constituents. The question is therefore whether the standards for drinking water need further revision or not. The main objective of this Special Issue is to help bridge the gap between knowledge on groundwater quality and its impact on human health.

This Special Issue invites researchers to submit relevant manuscripts focusing on the following aspects (but not limited to):

  • Medical geology and groundwater contamination
  • Organic solvents in groundwater and human health
  • Geochemical environment and human health
  • Links between geochemical environment and disease
  • Geochemical processes and effects on human health
  • Long-term health risk and pollution
  • Connections between groundwater quality and public health
  • Positive and negative societal impacts on groundwater quality
  • Land uses and groundwater quality
  • Groundwater quality changes and associated health risk effects
  • Earth material toxicity or deficiency and public health
  • Deficiency and toxicity of trace elements
  • Exposure to carcinogens via ingestion of groundwater
  • Chemical exposure through groundwater and health effects

Prof. Dr. Dimitrios E. Alexakis
Guest Editor

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Keywords

  • groundwater geochemistry
  • groundwater contamination
  • groundwater composition and human health risk
  • groundwater quality
  • inorganic compounds
  • organic compounds
  • trace elements
  • arsenic, antimony, chromium, microbes, radionuclides
  • groundwater protection and preservation
  • groundwater remediation
  • groundwater treatment technologies

Published Papers (12 papers)

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Research

19 pages, 2299 KiB  
Article
Characteristics and Impact Evaluation of Hydrological and Water Quality Changes in the Northern Plain of Cixi, Eastern China, from 2010 to 2022
by Yinghui Zhao, Mengyuan Jiang, Jing Cheng and Congfeng Jiang
Water 2024, 16(3), 489; https://doi.org/10.3390/w16030489 - 2 Feb 2024
Viewed by 889
Abstract
This paper analyzes the spatiotemporal changes and patterns of a regional water environment based on the hydrological and water quality monitoring times and the geographical locations of the monitoring sections in the research area, the plain of Cixi, eastern China. Based on the [...] Read more.
This paper analyzes the spatiotemporal changes and patterns of a regional water environment based on the hydrological and water quality monitoring times and the geographical locations of the monitoring sections in the research area, the plain of Cixi, eastern China. Based on the calculation of runoff generation and concentration in the coastal plain river network and based on the characteristics and impact evaluation of the regional water pollution, the migration and diffusion mechanisms of surface water pollutants were studied for different sources and characteristics of pollutants entering the river in different river sections. The analytic results show that the water environment and water resource security of the coastal plain mainly cause the problem of eutrophication in the water bodies, and the input of nitrogen and phosphorus from land sources is the main cause of eutrophication in the water bodies, mainly including the production and discharge of domestic sewage, nutrient loss in aquaculture water bodies, affecting agricultural activities, etc. The evaluation also demonstrates that with the development of coastal zones and the rapid development of coastal towns, as the population in coastal plain areas continues to increase, industrial development and population growth are the main driving factors for water quality changes. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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16 pages, 2845 KiB  
Article
Groundwater Environment and Health Risk Assessment in an In Situ Oil Shale Mining Area
by Xiaorong Wang, Boyue Liu, Shaolin He, Hongying Yuan, Dongli Ji, Ruolin Li, Yang Song, Wei Xu, Bo Liu and Yingjun Xu
Water 2024, 16(1), 185; https://doi.org/10.3390/w16010185 - 4 Jan 2024
Cited by 1 | Viewed by 1055
Abstract
To clarify the risk posed to groundwater in oil shale in situ mining areas, we examine five leached pollutants: Fe, Mn, Cr, sulfate, and ammonia nitrogen. Potential groundwater contents of these five pollutants were evaluated using an improved Nemero comprehensive index method and [...] Read more.
To clarify the risk posed to groundwater in oil shale in situ mining areas, we examine five leached pollutants: Fe, Mn, Cr, sulfate, and ammonia nitrogen. Potential groundwater contents of these five pollutants were evaluated using an improved Nemero comprehensive index method and a health risk assessment method. The results show that, compared with the Class III groundwater quality standard (GB/T 14848-2017) used in the People’s Republic of China, average values of Fe, Mn, and sulfate in leaching solution from Fuyu oil shale exceed the standard, while Cr and ammonia nitrogen do not exceed the standard, and the leaching solution is within Class V groundwater quality. The average values of Fe and Mn in the leaching solution from Fushun oil shale exceed the Class III standard, while Cr, sulfate, and ammonia nitrogen values from this oil shale do not exceed the standard, and the leaching solution is Class IV in terms of groundwater quality. The weighting value used in the Nemero assessment method for the heavy metal Cr is the largest as its potential to cause harm to groundwater quality is the largest. The weight value for sulfate is the smallest as the harm degree is the smallest. The chemical carcinogen Cr has the greatest potential impact on human health. The health risk caused by the chemical non-carcinogen Mn is greater than that caused by Fe and ammonia nitrogen. When high pyrolysis temperatures are used, Mn will be released into groundwater in large quantities. Therefore, supervision and control should be strengthened. The results presented here can provide a reference for the comprehensive evaluation of groundwater risks caused by in situ oil shale mining. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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34 pages, 21313 KiB  
Article
Integrated Assessment and Geostatistical Evaluation of Groundwater Quality through Water Quality Indices
by Iram Naz, Ijaz Ahmad, Rana Waqar Aslam, Abdul Quddoos and Andaleeb Yaseen
Water 2024, 16(1), 63; https://doi.org/10.3390/w16010063 - 23 Dec 2023
Cited by 6 | Viewed by 1416
Abstract
This study undertook an assessment of 24 physiochemical parameters at over 1094 sites to compute the water quality index (WQI) across the upper and central Punjab regions of Pakistan. Prior to the WQI calculation, an analytical hierarchy process (AHP) was employed to assign [...] Read more.
This study undertook an assessment of 24 physiochemical parameters at over 1094 sites to compute the water quality index (WQI) across the upper and central Punjab regions of Pakistan. Prior to the WQI calculation, an analytical hierarchy process (AHP) was employed to assign specific weights to each water quality parameter. The categorization of WQI into distinct classes was achieved by constructing a pairwise matrix based on their relative importance utilizing Saaty’s scale. Additionally, the groundwater quality status for irrigation and drinking purposes across various zones in the study area was delineated through the integration of WQI and geostatistical methodologies. The findings revealed discernible heavy metal issues in the Lahore division, with emerging microbiological contamination across the entire study region, potentially attributed to untreated industrial effluent discharge and inadequately managed sewerage systems. The computed indices for the Lahore, Sargodha, and Rawalpindi divisions fell within the marginal to unfit categories, indicating water quality concerns. In contrast, the indices for other divisions were in the medium class, suggesting suitability for drinking purposes. Scenario analysis for developing mitigation strategies indicated that primary treatment before wastewater disposal could rehabilitate 9% of the study area, followed by secondary (35%) and tertiary (41%) treatments. Microbiological contamination (27%) emerged as the predominant challenge for water supply agencies. Given the current trajectory of water quality deterioration, access to potable water is poised to become a significant public concern. Consequently, government agencies are urged to implement appropriate measures to enhance overall groundwater quality for sustainable development. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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16 pages, 2231 KiB  
Article
Improvement in Arsenic Adsorption and Calcite Dissolution Kinetics through Size Reduction of a Ferric Hydroxide-Calcite Adsorbent
by Lidia Fernandez-Rojo, Vicenç Martí, Irene Jubany, Neus Bahí, Marcel Janer, Xavier Martínez-Lladó and Miquel Rovira
Water 2024, 16(1), 30; https://doi.org/10.3390/w16010030 (registering DOI) - 21 Dec 2023
Viewed by 874
Abstract
The employment of granular ferric iron-(oxy)hydroxides, a well-known economic and effective method, lowers arsenic concentrations in different water types. However, for direct application in polluted groundwaters, there is a need to develop new injectable adsorbents for aquifers that could also neutralize acidic media. [...] Read more.
The employment of granular ferric iron-(oxy)hydroxides, a well-known economic and effective method, lowers arsenic concentrations in different water types. However, for direct application in polluted groundwaters, there is a need to develop new injectable adsorbents for aquifers that could also neutralize acidic media. In this context, a granular ferric hydroxide-calcite (GFH-C) adsorbent was size-reduced to 0.4–50 µm by sonication with the aim of improving (i) the adsorption of As(III) and As(V) at different pHs and (ii) the pH control through the dissolution of calcite. Batch experiments were conducted to determine As(III) and As(V) adsorption isotherms and kinetics, as well as calcite dissolution kinetics, using GFH-C of two sizes (granular and sonicated). Results showed that the arsenic binding capacity of sonicated adsorbents did not improve significantly. On the contrary, the As(III) and As(V) adsorption kinetics improved with the sonication, as in the case of calcite dissolution kinetics. The dissolution of calcite from the adsorbent made the water pH increase to around 9.2–9.4. The sonicated adsorbent offers an advantage in depolluting As-containing groundwater due to its smaller size, which is linked with faster arsenic adsorption and effective acidic water neutralization. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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13 pages, 3255 KiB  
Article
Human Adenovirus Detection and Genetic Characterization in Irrigation Water from the Riyadh Region, Saudi Arabia
by Abdulrahman Alkathiri, Saleh Eifan, Atif Hanif, Islam Nour, Abdullah E. Al-Anazi, Khalid Maniah, Riyadh Alotaibi and Yazeed Alharbi
Water 2023, 15(18), 3318; https://doi.org/10.3390/w15183318 - 20 Sep 2023
Viewed by 1245
Abstract
Adenoviruses are considered one of the most persistent enteric pathogens that can penetrate entire aquifer matrices. An ongoing monitoring of irrigation water is essential to mitigate potential public health risks. We investigated the prevalence of human adenoviruses (HAdV) in the groundwater discharge basins [...] Read more.
Adenoviruses are considered one of the most persistent enteric pathogens that can penetrate entire aquifer matrices. An ongoing monitoring of irrigation water is essential to mitigate potential public health risks. We investigated the prevalence of human adenoviruses (HAdV) in the groundwater discharge basins of Aluraiji (AW-DB) and Diriyah (DW-DB) and in the irrigation water of Al Harriq (H-IW) and Al Hayer (AH-IW) from January to December 2021. The meteorological impact (temperature, relative humidity, and wind speed) on HAdV prevalence and molecular diversity was investigated by targeting a selected region of the Hexon gene. The samples were concentrated using the polyethylene glycol precipitation (PEG) method. HAdVs were detected using PCR and sequenced by Sanger sequencing, and phylogenetic analysis was performed. The highest HAdV prevalence was recorded in H-IW, AH-IW, and DW-DB (100%). HAdV sequences were found to be closely related to species F (type 41) with a predominance of the 00-2B64 sequence (86.4%). Phylogenetic analysis depicted a close relationship of this study’s isolate 00-2B64 to a Brazilian and Saudi isolate, whereas 08-2B64 was found to be related to a sequence from an AnNazim landfill (LF1; d = 0.00) from Riyadh, Saudi Arabia. A high HAdV prevalence was recorded at a temperature range of 19–28 °C, wind speed was recorded at a range of (16–20 km/h), and relative humidity was recorded at a range of (15–25%). Meteorological variations exhibited no significant effect on the prevalence of HAdVs. The findings provided data on HAdV prevalence and predominant species in the irrigation water of Riyadh, Saudi Arabia and presented information regarding the environmental effects of HAdV persistence. In public health contexts, this will help in the planning of disease control strategies. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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15 pages, 6486 KiB  
Article
Groundwater–Surface Water Exchange and Spatial Distribution of Arsenic in Arid and Semi-Arid Regions: The Case of Aksu River in Xinjiang, Northwestern China
by Fengjun Shao, Wenfeng Wang and Jing He
Water 2023, 15(13), 2391; https://doi.org/10.3390/w15132391 - 28 Jun 2023
Viewed by 1104
Abstract
The Aksu River, a quintessential inland river, exhibits elevated arsenic (As) concentrations in certain sections of its natural waters. Further investigation is necessary to determine the role of surface water and groundwater (SW-GW) exchanges in contributing to these high As concentrations. Both surface [...] Read more.
The Aksu River, a quintessential inland river, exhibits elevated arsenic (As) concentrations in certain sections of its natural waters. Further investigation is necessary to determine the role of surface water and groundwater (SW-GW) exchanges in contributing to these high As concentrations. Both surface water and groundwater constitute crucial components of the basin water cycle, and the interaction between the two has been a central focus in basin water cycle research. In this study, a total of 59 groundwater samples and 41 surface water samples were collected along the river’s course within the basin. Among the groundwater samples, 18.64% exceeded the permissible drinking limit for As concentrations (10 μg/L), while 39.02% of the surface water samples exceeded this threshold. The water bodies in the Aksu River Basin are mildly alkaline, with total dissolved solids (TDSs) in surface water significantly surpassing those in groundwater. The chemical compositions of surface water and groundwater are strikingly similar, with the predominant anions being chloride (Cl) and sulfate (SO42−) and the principal cations being sodium (Na+). The dissolution of silicate and carbonate minerals primarily influences the water chemistry characteristics of surface water and groundwater in the Aksu River Basin, followed by the dissolution of salt rocks. Human activities also play a major role in affecting the river’s water quality. The distribution of groundwater with elevated As content is entirely encompassed within the spatial distribution of surface water. Groundwater–surface water exchange plays a vital role in As enrichment in surface water. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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15 pages, 4110 KiB  
Article
Fluorine-Rich Shallow Groundwater in Weigan River Basin (Xinjiang): Enrichment Factors and Spatial Distribution
by Tianchao Liu, Fengjun Shao, Zizhao Zhang and Tong Li
Water 2023, 15(5), 926; https://doi.org/10.3390/w15050926 - 27 Feb 2023
Cited by 3 | Viewed by 1284
Abstract
Long-term usage of drinking water with excessive fluoride concentration (above 1.5 mg/L) is known to harm human health. Since the fluoride concentration in the shallow groundwater of the Weigan River Basin, China, exceeds this level, this study explored fluoride’s sources and enrichment mechanism [...] Read more.
Long-term usage of drinking water with excessive fluoride concentration (above 1.5 mg/L) is known to harm human health. Since the fluoride concentration in the shallow groundwater of the Weigan River Basin, China, exceeds this level, this study explored fluoride’s sources and enrichment mechanism for this basin. Based on information retrieval and regional geological environment analyses, 47 sets of shallow groundwater samples in the Weigan River Basin were collected and analyzed. The research results show that the fluoride content in the drainage basin of the research area ranged from 0.2 to 5.46 mg/L, with an average value of 1.14 mg/L. The test results showed that 40.43% of the water sample test results exceeded the national domestic drinking water safety standard (1.0 mg/L). The average pH value of the research area was 8.37, which was slightly basic. Type Na+–Cl/(SO42−) was the primary hydrochemical type. In the research area, groundwater with a high fluoride concentration contained much sodium and little calcium. The main mechanism of excessive fluoride formation in the groundwater was the continued dissolution of fluorine-containing minerals (fluorite) in the research area, while the main fluorine source was weathering of silicate rocks and evaporites. Evaporation-crystallization and cation exchange were the main factors controlling fluorine enrichment. These findings indicate that physicochemical processes are the major mechanisms for controlling F enrichment and that may be useful for studying F occurrence in groundwater in arid and semi-arid areas. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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21 pages, 14883 KiB  
Article
Groundwater Quality and Potential Health Risk in Zhambyl Region, Kazakhstan
by Dinara Adenova, Sultan Tazhiyev, Janay Sagin, Malis Absametov, Yermek Murtazin, Ludmila Trushel, Oxana Miroshnichenko and Abdulhalim Zaryab
Water 2023, 15(3), 482; https://doi.org/10.3390/w15030482 - 25 Jan 2023
Cited by 2 | Viewed by 2209
Abstract
Securing water resources is a complicated issue in Kazakhstan. Only 36% of Kazakhstan’s rural population has access to a centralized water supply and 57.3% use groundwater accessed by wells and boreholes. The groundwater quality must be monitored to minimize health risks. The aim [...] Read more.
Securing water resources is a complicated issue in Kazakhstan. Only 36% of Kazakhstan’s rural population has access to a centralized water supply and 57.3% use groundwater accessed by wells and boreholes. The groundwater quality must be monitored to minimize health risks. The aim of this project is to investigate the groundwater quality in the Zhambyl region of Kazakhstan. Groundwater depletion, pollution, waterlogging, and salinization are all widespread in Kazakhstan. Previously, 500 self-flowing and, within this project, 204 wells were investigated in southern Kazakhstan, the Zhambyl region. The field works and data processing was carried out in three phases: first, a fieldwork survey of existing water wells; the second phase, field work with more detailed hydrogeological investigations, including measurements of flow rates, pH, temperature, and electrical conductivity of water samples; the third phase, processing, and analysis of field data samples in chemical laboratories. Kazakhstan’s requirements for drinking water are much lower than the requirements in the EU. Less than 30% of Kazakhstan’s population has access to safe water and about 50% of the population consumes drinking water that does not meet international standards of salinity, hardness, or bacteriological levels. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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15 pages, 3066 KiB  
Article
Bioremediation of Chromium-Contaminated Groundwater Using Chromate Reductase from Pseudomonas putida: An In Silico Approach
by Munazzah Tasleem, Abdel-Aziz A. A. El-Sayed, Wesam Mekawy Hussein and Abdulwahed Alrehaily
Water 2023, 15(1), 150; https://doi.org/10.3390/w15010150 - 30 Dec 2022
Cited by 7 | Viewed by 2515
Abstract
Chromium is a toxic heavy metal abundantly present in the environment, specifically in groundwater. The groundwater in Saudi Arabia was assessed for heavy metal presence; chromium was detected at a high concentration in Madinah. Many researchers have used various bioprocesses over the last [...] Read more.
Chromium is a toxic heavy metal abundantly present in the environment, specifically in groundwater. The groundwater in Saudi Arabia was assessed for heavy metal presence; chromium was detected at a high concentration in Madinah. Many researchers have used various bioprocesses over the last few decades to mitigate Cr(VI) toxicity. The genus Pseudomonas member Pseudomonas putida is widely dispersed in the natural environment. P. putida is chromate-resistant and has a high chromate reduction rate. Bioremediation procedures can eradicate the most potently toxic metal, Cr(VI), in water, air, and soil. Chromate reductase (ChrR) is a bacterial enzyme from P. putida that can be utilized in bioremediation to remove chromate from the environment in a cost-effective and environmentally safe approach. To comprehend the role of ChrR in reducing Cr(VI) to Cr(III), a thorough sequence analysis was followed by constructing models for wild-type and mutants by applying several homology modeling techniques. The protein structure quality of the generated models was evaluated, and the best model was adopted for further optimization by employing an energy minimization technique. Molecular docking studies investigated the intra-molecular interaction between wild-type and mutant ChrR and Cr(VI). Our study is a novel method for determining the 3D structure and interaction of ChrR with Cr(VI) to convert it to a less hazardous form (III). Additionally, it provides stable mutants: Arg83Trp, Gly124Ile, and His127Trp, with a high binding affinity for Cr(VI), which can be considered for protein engineering to produce stable and efficacious enzymes to reduce Cr(VI) to a less toxic form. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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16 pages, 854 KiB  
Article
Heavy Metals, Pesticide, Plasticizers Contamination and Risk Analysis of Drinking Water Quality in the Newly Developed Housing Societies of Gujranwala, Pakistan
by Habib ur Rehman, Masooma Munir, Kamran Ashraf, Komal Fatima, Sana Shahab, Baber Ali, Fatimah A. Al-Saeed, Ahmed M. Abbas and Qamar uz Zaman
Water 2022, 14(22), 3787; https://doi.org/10.3390/w14223787 - 21 Nov 2022
Cited by 10 | Viewed by 3391
Abstract
The supply of clean drinking water is essential for a healthy life, but access to safe and healthy drinking water has become a key issue worldwide, especially in developing nations such as Pakistan. This research work focused on investigating the suitability of groundwater [...] Read more.
The supply of clean drinking water is essential for a healthy life, but access to safe and healthy drinking water has become a key issue worldwide, especially in developing nations such as Pakistan. This research work focused on investigating the suitability of groundwater by measuring quality parameters, identification of pesticide pollutants, and health risk analysis in adults and children due to the consumption of groundwater in recently developed housing societies of the Gujranwala district, Punjab, Pakistan. Drinking water samples (n = 200) were collected from electric water pumps and analyzed by in situ testings following the Standard American Public Health Association (APHA) methods. Pesticides and plasticizers detection was carried out using gas chromatography-mass spectrometry (GC/MS). Results showed that the concentrations of dissolved Cr and Pb at more than 20% of sampling sites exceeded the allowable limit of the World Health Organization (WHO). However, the measured physico-chemical attributes and concentrations of Fe and Zn did not exceed their respective permissible limits. The most abundant pollutants detected were plasticizers (30); followed by herbicides (21); fungicides, acaricides, and insecticides (16); and various types of plant growth regulators (7). Differential patterns for the hazard quotient (HQ) and hazard indices (HI) were observed, of which were above the WHO limits. The decreasing order of the hazard quotient was Cl > Zn > Mg > Cr > Pb for both adults and children. In crux, the quality of water is poor for drinking purposes and the safety and well-being of residents in the recently developed housing societies of the study area may be at risk. Hence, it is important to implement a plan for water quality management, and the regular monitoring (periodic testing of qualitative and quantitative attributes) of the water quality to overcome health-related issues. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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15 pages, 4297 KiB  
Article
An Integrated Bayesian and Machine Learning Approach Application to Identification of Groundwater Contamination Source Parameters
by Yongkai An, Yanxiang Zhang and Xueman Yan
Water 2022, 14(15), 2447; https://doi.org/10.3390/w14152447 - 7 Aug 2022
Cited by 5 | Viewed by 2049
Abstract
The identification of groundwater contamination source parameters is an important prerequisite for the control and risk assessment of groundwater contamination. This study developed an innovative approach for the optimal design of observation well locations and the high-precision identification of groundwater contamination source parameters. [...] Read more.
The identification of groundwater contamination source parameters is an important prerequisite for the control and risk assessment of groundwater contamination. This study developed an innovative approach for the optimal design of observation well locations and the high-precision identification of groundwater contamination source parameters. The approach involves Bayesian theory and integrates Markov Chain Monte Carlo, Bayesian design, information entropy, machine learning, and surrogate modeling. The optimal observation well locations are determined by information entropy, which is adopted to mine valuable information about unknown groundwater contamination source parameters from measurements of contaminant concentration according to Bayesian design. After determining the optimal observation well locations, the identification of groundwater contamination source parameters is implemented through a Bayesian-based Differential Evolution Adaptive Metropolis with Discrete Sampling–Markov Chain Monte Carlo approach. However, the processes of both determination and identification are time-consuming because the original simulation model (that is, the contaminant transport model) needs to be invoked multiple times. To overcome this challenge, a machine learning approach, that is, Multi-layer Perceptron, is used to build a surrogate model for the original simulation model, which can greatly accelerate the determination and identification processes. Finally, two hypothetical numerical case studies involving homogeneous and heterogeneous cases are used to verify the performance of the proposed approach. The results show that the optimal design of observation well locations and high-precision identification of groundwater contamination source parameters can be implemented accurately and effectively by using the proposed approach. In summary, this study highlights that the integrated Bayesian and machine learning approach provides a promising solution for high-precision identification of groundwater contamination source parameters. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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17 pages, 2508 KiB  
Article
Characterisation of Hydro-Geochemical Processes Influencing Groundwater Quality in Rural Areas: A Case Study of Soutpansberg Region, Limpopo Province, South Africa
by Lindelani Lalumbe and Thokozani Kanyerere
Water 2022, 14(12), 1972; https://doi.org/10.3390/w14121972 - 20 Jun 2022
Cited by 6 | Viewed by 2630
Abstract
Groundwater is often the main or only source of fresh water supply in arid to semi-arid rural areas owing to decreasing rainfall patterns, reduced availability of surface water and socioeconomic activities. It is important to understand the hydro-geochemical processes influencing groundwater quality for [...] Read more.
Groundwater is often the main or only source of fresh water supply in arid to semi-arid rural areas owing to decreasing rainfall patterns, reduced availability of surface water and socioeconomic activities. It is important to understand the hydro-geochemical processes influencing groundwater quality for improved management and sustainability of resources and to improve rural livelihoods. To understand the hydro-geochemical process influencing the hydro-geochemistry of the Soutpansberg region, this study assessed groundwater quality data from 12 boreholes and 2 geothermal springs collected between 1995 and 2017. This study indicated that the majority of the samples were classified as fresh groundwater dominated by Ca-HCO3 and mixed Ca-Mg-Cl types. Gibbs diagrams, Pearson correlations, bivariate plots and saturation indexes suggested that rock dominance processes, such as weathering of silicates, dissolution of carbonates and halite minerals and ion exchange processes, were the main hydro-geochemical processes influencing the groundwater quality in the Soutpansberg region. The high concentration of F in the geothermal spring was attributed to the dissolution of fluorite mineral. Point source anthropogenic inputs from fertilisers were attributed to the high concentration of NO3 in the groundwater. This study recommends that research outputs should be used to influence and support policy change and groundwater allocation in arid to semi-arid rural environments for improved management of resources and livelihoods. This study further recommends that suitable deflouridation and denitrification techniques be applied to improve the quality of groundwater for drinking purposes. Full article
(This article belongs to the Special Issue Groundwater Quality and Human Health Risk)
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